A tiger escaped its cage, killed a visitor and mauled two others Tuesday evening at the San Francisco Zoo in a shocking Christmas Day attack about a year after another mauling.

Police shot and killed the tiger outside the zoo's Terrace Cafe shortly after the park closed to visitors at 5 p.m.

They encountered the tiger mauling a man who was covered in blood, said San Francisco Police Department Sgt. Steve Mannina. When officers tried to intervene, the tiger turned and headed toward them, prompting several officers to fire numerous shots at the tiger.

The dead tiger remained outside the cafe as darkness fell over the zoo. Two others mauled by the tiger were rushed to the hospital with critical injuries.

The zoo, festooned with holiday decorations was silent after the attacks, save for police helicopters and police officers sweeping the grounds for potential additional victims.

"We won't know until tomorrow whether this was negligence or intentional or how the tiger got out," Mannina said.

Some zoo employees in the gift shop locked themselves in as they had been instructed in case of emergency, but would not comment further.

According to the zoo's website, the zoo has two Siberian tigers, Tony and Tatiana, who live in an outdoor enclosure near the Lion House. It also has a female Sumatran tiger, Padang, at the west end of the Lion House. It was not immediately clear which tiger escaped.

The attack occurred about a year after a 350-pound Siberian tiger named Tatiana attacked and seriously injured keeper Lori Komejan during a regular afternoon feeding.

The California Division of Occupation Safety and Health later ruled the zoo was responsible for that incident because of poor training and how the cages were set up.

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